Conventionally, an orientation control and a torque control of a cutter drum in a small diameter pipe shielding machine or an excavating type underground advancing machine have been performed relying on perception and experience of operators.
FIG. 26 shows the conventional method of control for the advancing machine, in which steps of detecting errors in vertical and horizontal directions, pitching angle, yawing angle of an excavation head by means of a sensor group, and of determination of a rocking magnitude according to a judgement of the operator based on the detected data are performed during an interval between "rear propelling jack contraction" and "rear propelling pin insertion". The rocking magnitude of a cutter drum is controlled on the basis of the determined value.
On the other hand, at this time, a hydraulic pressure of an actuator for rotatingly driving the cutter drum is constantly monitored for performing control operation of the cutter torque while the rear propelling jack is advanced.
In the above-mentioned conventional control method, a problem is encountered in significant variation of a precision in construction of a tunnel depending upon the skill of the operator for reliance to the operators' perception and experience, as set forth above.